Mechanism of action of doxycyclinedoxycycline is a broad spectrum antibiotic which acts against both gram positive and gram negative organisms. it exerts its bacteriostatic action by accumulating inside the bacteria through specific transporter protein and by passive diffusion & inhibits bacterial protein synthesis by attaching to 30 s subunit of bacterial ribosome (which are absent in mammals).doxycycline interfering the attachment of aminoacyl-trna to the mrna-ribosome complex and peptide chain fails to grow. it chelates cations like ca &mg and inhibits functioning of various enzymes & ribosome. mechanism of action of ambroxolambroxol hydrochloride acts as an expectoration improver and mucolytic agent. it decreases mucus viscosity by altering its structure. it depolymerises mucopolysaccharides directly as well as by liberating lysosomal enzymes and by breaking network of fibres in tenacious sputum . it induces thin copious bronchial secretion and possesses antioxidant propertie